I have a Stewart Warner 9152-C radio that I picked up at a flea market. The radio intially would not play without a buzz. I replaced the electrolytic and regular caps and I thought I was home free. My problem is that the radio plays fine for about 30 seconds to a few minutes and then the audio distorts and the volume sporadically goes up and down. Since I do not have a tube tester, I replaced each tube except for the output 50B5 tube, which I did not have an extra of. Any suggestions? Could it be the output tube.

Hi Steve

The most common problem for distortion is grid #1 coupling cap to your 50B5 being leaky. Replace the cap connected to pin #1 or #7 on your 50B5 if you haven't already. Also check the resistor on one of these pins. It should not be over 500K in value. Replace the resistor if it has gone much higher.

The 50B5 can be bad but start with coupling cap and resistor first.

Norm

:I have a Stewart Warner 9152-C radio that I picked up at a flea market. The radio intially would not play without a buzz. I replaced the electrolytic and regular caps and I thought I was home free. My problem is that the radio plays fine for about 30 seconds to a few minutes and then the audio distorts and the volume sporadically goes up and down. Since I do not have a tube tester, I replaced each tube except for the output 50B5 tube, which I did not have an extra of. Any suggestions? Could it be the output tube.

Thanks for the info. I will try it tomorrow.
steve

:Hi Steve
:
: The most common problem for distortion is grid #1 coupling cap to your 50B5 being leaky. Replace the cap connected to pin #1 or #7 on your 50B5 if you haven't already. Also check the resistor on one of these pins. It should not be over 500K in value. Replace the resistor if it has gone much higher.
:
: The 50B5 can be bad but start with coupling cap and resistor first.
:
:Norm
:
:
:
::I have a Stewart Warner 9152-C radio that I picked up at a flea market. The radio intially would not play without a buzz. I replaced the electrolytic and regular caps and I thought I was home free. My problem is that the radio plays fine for about 30 seconds to a few minutes and then the audio distorts and the volume sporadically goes up and down. Since I do not have a tube tester, I replaced each tube except for the output 50B5 tube, which I did not have an extra of. Any suggestions? Could it be the output tube.

Usually you can get by without replacing the condenser on the volume control. If the problem doesn´t go away after replacing the 50B5 control grid condenser, replace the condenser on the volume control as well. Also consider replacing the tone condenser (connects to plate of 50B5). If one condenser is leaky, the rest are likely to be leaky as well. Leakage at any of the audio condensers can cause audio distortion, though the one that Norm mentioned is the most likely cause.

Thomas